The present invention relates to a yarn winding apparatus of the type comprising a winding spindle which is rotated about a fixed axis and which is adapted to coaxially mount a bobbin tube for receiving the yarn, and so as to form a wound package thereon. Also, the apparatus includes a yarn traversing mechanism which is mounted in a slide which is adapted to move radially away from the spindle as the package builds on the bobbin tube.
Winding apparatus of the described type are known wherein the bobbin tube which is mounted on the spindle is rotatably driven by contact with a drive roll, note for example DE-OS No. 25 44 773 and U.S. Pat. No. 4,106,710. In order to apply the necessary driving force to the surface of the package as the diameter increases, there is provided means for regulating the pressure of the contact roll against the surface of the package, and which includes a pneumatic control by which a nominal value can be determined. In most instances, the slide is vertically movable, but according to one of the embodiments of the above described patents, the traversing slide is horizontally movable and incudes similar contact pressure regulating means. In the case of a yarn winding apparatus having a surface driven winding spindle, the contact pressure between the contact roll and the package needs to be accurately controlled, so as to prevent the sensitive layers of yarn on the surface of the package from being damaged by too much slippage. However, in the case of directly driven winding spindles, it is not usually necessary to control the contact pressure for these functional reasons.
Precision package winding apparatus are also known, in which the slide mounting the traversing mechanism is moved radially from the axis of the winding spindle, or along a circular arc about a fulcrum. The slide typically mounts a contact roll which is pressed against the surface of the package by for example a compensating weight, note U.S. Pat. No. 3,480,218, or by a resilient biasing means, note DE-OS No. 2,937,600, or by a cylinder-piston drive, note U.S. Pat. No. 3,717,311. The contact pressure serves to dampen the fluctuations which result from the movement of the slide. In addition, it has been found that the package build is advantageously influenced, when the pressure between the contact roll of the slide and the package surface is distributed over the entire axial length of the package.
It is accordingly an object of the present invention to provide a yarn winding apparatus of the described type and wherein the contact pressure between the contact roll supported in the slide and the surface of the package may be controlled by a relatively simple mechanical mechanism.
It is also an object of the present invention to provide a yarn winding apparatus of the described type wherein the contact pressure can be selected and controlled in accordance with the winding conditions, and preferably in a manner so that the pressure decreases during the build of the package.